Monday, 2 November 2009

Science Fact of the Week 33 - Megalodon

Megalodon, or Carcharodon megalodon, was a giant shark which lived from roughly 25 million to 1.6 million years ago, during the Miocene and Pliocene epochs. It is now thankfully extinct, but the exact time of its extinction is hotly debated. Megalodon was a shark that may have been over 15 m in length. This is at least three or four times as long as the great white shark, but this is only an estimate made from many fossilized teeth and a few fossilized vertebrae that have been found. These giant teeth are the size of a person's hand! No other parts of this ancient shark have been found, so we can only guess what it looked like. Since megalodon's teeth are very similar to the teeth of the great white shark (but bigger and thicker), it is thought that megalodon may have looked like a huge, streamlined version of the great white shark.

Megalodon's diet probably consisted mostly of whales. Sharks eat the equivalent of about 2 percent of their body weight each day; this a bit less than a human being eats. Since most sharks are cold-blooded, they don't have to eat as much as us (a lot of our food intake is used to keep our bodies warm). Shark fossils are extremely rare because sharks have no bones, only cartilage, which does not fossilize well. Their teeth, however, are made of a bone-like material coated with hard enamel and they fossilize very well. Megalodon's jaws could open 1.8 m (6 feet) wide and 2.1 m (7 feet) high. The jaws were loosely attached by ligaments and muscles to the skull, opening extremely wide in order to swallow enormous objects. It could easily swallow a large great white shark whole!

Like most sharks, megalodon's teeth were probably located in rows which rotated into use as they were needed. Most sharks have about 3-5 rows of teeth at any time. The front set does most of the work. The first two rows are used for obtaining prey, the other rows rotate into place as they are needed. As teeth are lost, broken, or worn down, they are replaced by new teeth. Megalodon may have had hundreds of teeth at one time. It did not chew their food like we do, but gulped it down whole in very large chunks.

How megalodon became extinct is a bit of a mystery, as it is considered one of the best predators to ever have existed on this planet. However, it is hypothesised that climatic changes caused whales, megalodon’s main prey, to migrate to the colder water of the Arctic and Antartic, water much too cold for megalodon to survive in.